Field of the Invention
The invention relates to a semiconductor device and more particularly to a seal ring structure with a capacitor.
Description of the Related Art
In the manufacturing of integrated circuits (ICs), seal ring (also called as a guard ring) formation is an important part for semiconductor processes. A semiconductor device such as an IC is manufactured in a form of a chip cut out from a semiconductor wafer having an IC pattern formed thereon. A plurality of chips are formed by dicing the semiconductor wafer. In the dicing process, semiconductor chips are separated from each other, and mechanical stress such as vibration is usually applied to the semiconductor substrate/wafer. Accordingly, a crack on the chip may be caused when the dicing process is performed.
Moreover, a plurality of semiconductor elements are formed on the semiconductor substrate. At this time, stacked insulating films, such as intermetal dielectric (IMD) films and/or interlayer dielectric (ILD) films, deposited during formation of the semiconductor elements are exposed from the cut section of the dicing line portions. These stacked insulating films and interfaces therebetween create paths for moisture to penetrate, and may cause a malfunction of the semiconductor device.
In order to prevent semiconductor chips from damage caused by the dicing process and from moisture-induced degradation, a seal ring structure is provided between an IC pattern region and a dicing line of each chip. A conventional seal ring structure is formed in the process for forming wiring layers and contact portions and is a multi-layer structure composed of alternating metal and insulating layers. Vias are formed in each of the insulating layers to provide electrical paths between adjacent metal layers. However, the lowermost metal layer in the seal structure electrically contacts with the semiconductor substrate and thus creates a substrate short-circuit path around the semiconductor chip. The seal ring structure provides a very low resistance metal path around the periphery of the semiconductor chip, such that noise can travel from the IC region of the semiconductor chip to the seal ring structure, resulting in the substrate noise coupling issue.
Accordingly, there is a need to develop a novel seal ring structure which is capable of mitigating or eliminating the aforementioned problem.